1. Field of the Invention
The invention concerns a reading unit for a magnetic domain propagation register on a soft magnetic layer. It applies to memories for digital computers according to the thin layer technique.
2. Description of the Prior Art
Since several years ago, it is known that the thin layer technique can be used for constituting shift registers (see, for example, U.S. Pat. No. 2,919,432). The digital data is propagated in the form of magnetization domains anti-parallel to a general magnetizing direction on a ferro-magnetic layer having uniaxial anisotropy.
At the output of a register, reading devices must transform the data contained in the magnetization into an electric signal. For that purpose, inductive or galvanometric phenomena such as magnetoresistance or, even, the plane Hall effect (see, for example, the article which appeared in IEEE Transactions on Magnetics Vol MAG 6 -- No. September 1970, p. 451-463 and IEEE Transactions on Magnetics September 1971 p. 365-369).
The invention aims at proposing a reading unit which can be manufactured in the same way as actual shift registers, that is, by successive deposits of the magnetic, insulating and conductive layers which are adapted to selective reading of one unit among a number of existing units and which make it possible to distinguish easily between the two possible magnetization states. The unit according to the invention uses the magnetoresistance effect which, it is known, is insensitive to a change in the orientation of the magnetization through 180.degree.. This difficulty has been overcome up till now for example by laying the output channel at 45.degree. in relation to the easy axis of the magnetization in the thin layer of the register and by arranging the power points and the reading conductors on the outside of the channel. This arrangement requires a large space on the substrate of the register and therefore opposes the manufacturer's wish to increase the density of the data in the register.